Natural vegetable fats predominantly have a liquid consistency at ambient temperature. When a more solid consistency is needed, e.g. for the manufacture of plastic emulsion spreads, a hardstock fat is incorporated in the oil. In a processed W/O-emulsion spread the oil phase consists of a liquid oil which is structured with a lattice of hardstock fat crystals. By structuring the fat phase the spread obtains the desired plasticity and emulsion stability. The quality of the hardstock fat and the amount needed for oil structuring are inversely related.
Natural vegetable fats which have hardstock functionality are rare. Natural fats in the context of this specification are fats which as such are present in their non-genetically modifified source organism, particularly in the seeds or fruits of particular plants. For acting as hardstock fat such non-processed vegetable fats usually lack the necessary high content of saturated fatty acids with a chain length of at least 16 carbon atoms. Shea fat, cocoa butter and palm oil are the few examples of fats containing a substantial amount of saturated fatty acid.
Cocoa butter is the only unprocessed fat which contains a relatively high amount of saturated fatty acid and which as such has been used for margarine production. However, use of cocoa butter as hardstock fat for spread preparation entails serious disadvantages. Cocoa butter has a high content of palmitic acid. Further, products prepared with cocoa butter suffer from severe re-crystallisation phenomena. In chocolate these become apparent as fat blooming. Coarse grains are feared in spread preparation since these would easily spoil the product's consistency. Finally, cocoa butter generally is too expensive to serve as hardstock fat in margarine manufacture.
Palm oil to the contrary is cheap, but has other disadvantages. It needs modification before it is suited for use as first class hardstock fat. On its own its structuring functionality is insufficient for the manufacture of good products. The relatively low level of saturated fatty acids (<50 wt. %), their unfavourable distribution over the constituting triacylglycerides and the relatively high content (>15 wt. %) of polyunsaturated fatty acids make it necessary to subject palm oil to an oil modification process. Besides its insufficient structuring ability, palm oil also suffers from the abundant presence of POP and PPO type triglycerides that post-crystallize as undesired fat grains in the final fat spread.
So palm oil has to be subjected to either hydrogenation or fractionation in order to increase the level of saturated fatty acids. Both techniques result in structuring fats which cause a prohibitively bad oral response. Consequently, the resulting fats are typically used only as a supplement to other main hardstock fats or as a component in an interesterification mixture. Such interesterification mixture usually contains a further fat rich in medium chain (C12 or C14) saturated fatty acids such as palmkernel fat or coconut fat. In this way effectively structuring fat compositions can be manufactured. They typically contain as main structuring triglycerides the triglyceride categories HHH, H2M, H2U, and HM2, where H denotes saturated fatty acid residues with more than 15 carbon atoms, M saturated fatty acid residues with 12 or 14 carbon atoms (the above mentioned medium chain saturated fatty acids) and U any unsaturated fatty acid residue with more than 15 carbon atoms.
The properties of the resulting interesterified triglyceride mixture can be manipulated by the man skilled in the art through a proper choice of the three involved fat types: the fat containing medium chain triglycerides, the fat with a high content of palmitic acid residues and, optionally, the liquid oil such as rapeseed oil or sunflower oil. With a high palm fat component, said manipulation yields a triglyceride profile in which palmitic acid residues predominantly are the fatty acid residues denoted as H, the residues M predominantly are lauric acid residues and the fatty acid residues of the group U contain significant portions of both mono- and polyunsaturated C17+ fatty acid residues.
One of the options to vary the the medium chain triglycerides containing fat has been described in U.S. Pat. No. 6,238,723. Use is made of high lauric rapeseed oil which has resulted from biotechnological developments based on genetical modification of rapeseed. The high lauric oil is interesterified with a fat with a high content of C16+ fatty acids, such as palmitic acid or stearic acid. Only fats which have been hydrogenated or fats which have been obtained by genetical modification have been indicated to be suitable for such interesterification.
Although with palm oil after proper modification a hardstock fat can be obtained which is quite satisfactory from the point of view of good structuring ability and of ensuring a good mouthfeel of the final spread product, this natural fat, just like cocoa butter, unfortunately suffers from an undesirably high content of palmitic acid.
A high content of palmitic acid residues has been established to contribute to a high Keys value. A fat's Keys number, is a measure for the nutritional effect of fat intake on blood cholesterol level and thus is a risk indicator for affecting cardiovascular health. A high Keys value means that consumption of the fat adversely affects the blood cholesterol level.
A structuring fat necessarily contains a high level of saturated fatty acid. However, the only option for avoiding palmitic acid is stearic acid.
Presently, raising the content of stearic acid residues in a vegetable fat can be accomplished only by hydrogenating an unsaturated vegetable oil, by fractionation of specific vegetable fats or by genetical modification of the oil source plant. Hydrogenation, however, presently is avoided for fat processing since it conflicts with the naturalness requirement. Equally oils resulting from genetical modification are qualified as non-natural. The use of fractionation as described hereinbefore for the upgrading of palm oil, is not desired either, since such fractionation inherently results in the generation of a secondary product stream which has to be disposed of. Moreover the only vegetable stearic acid containing fat which delivers a suitable fractionated fat is said shea fat and not without necessarily refining by wet fractionation which process is considered non-natural and which makes shea fat too expensive for use in common spread manufacture.
According to co-pending not-prepublished patent applications EP00204120.0 and EP01201916.2 it was found that some natural high stearic fats are suited as hardstock fat for the preparation of edible W/O-emulsion spreads. Although the fats as such were known since long, their use for the manufacture of edible emulsion spreads was not yet recognized and particularly not their oil structuring ability.
Surprisingly, these fats, when refined, can be used without any modification. Fractionation is mentioned as an option, where the natural variant, particularly dry fractionation is preferred.
Patent application WO 97/28695 discloses an interesterification process which employs as sole fat a non-hydrogenated high stearic oil. Its content of stearic acid residue is 15–45%. The process delivers specific fat compositions with a favourable ratio of (HHO+HOH) to (HHL+HLH) triglycerides which is <1.0.
O denotes oleic acid residues and L residues of poly-unsaturated fatty acids. H is as defined before. When selecting the high stearic starting oil, only an oil obtained by genetical modification has been indicated. Application of this procedure to the high stearic fats mentioned in patent applications EP00204120.0 and EP01201916.2, yields hardstock fats which cause a prohibitively bad mouthfeel and a ratio of (HHO+HOH) to (HHL+HLH) triglycerides >1.0.
The present invention provides oils which have been obtained neither by hydrogenation nor by genetical modification. It provides a process for modifying and improving the structuring quality, the manufacturability and processability of high stearic fats, which process may be qualified as natural.